Electrical timing apparatus



June 5, 1956 c. H. FLUBACKER 2,749,404

ELECTRICAL TIMING APPARATUS Filed Aug. 8, 1952 INVENTOR.

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JZA ZyzM A United rates ELECTRICAL TIMING APPARATUS Charles H.Flubacker, Chicago, lllL, assignor to Cook Electric Company, Chicago,Ill., a corporation of llliuois A Application August 3, 1952, Serial No.303,297

4 Claims. (ill. 200-413) This invention relates to electrical timingapparatus and more particularly to thermally actuated timing apparatusdesigned to control various extrinsic electrical circuits.

it is a principal object of this invention to provide new and improvedtiming apparatus for intermittently completing various electricalcircuits.

it is a further object of this invention to provide such improvedapparatus which is extremely rapid in operation and requires minuteoperating currents.

The apparatus heretofore employed in intermittently making and breakingelectrical circuits in response to changes in current in a controlcircuit have generally incorporated either a magnetic coil and contactsmounted on a movable armature or contacts actuated by the deformation ofa bimetallic strip. The electromagnetic type of device is not wellsuited for use where severe shocks are encountered, or where extremes ofhumidity and other atmospheric conditions may exist. The bimetallicelement is relatively immune to shocks and vibration and is notadversely affected by high humidity but has a relatively large powerrequirement and a substantial thermal delay.

in aircraft operations, it is extremely important that a switchingmechanism of this type utilize extremely small currents for actuationand also be immune to the deleterious effects of motion, vibration, andvarious other shocks. it is further desirable that such switchingapparatus be extremely light in weight, as many such devices may benecessary in an airplane and weight conservation is one of thefundamental concerns in the design of aircraft ap paratus.

Therefore it is a further object or" this invention to provide extremelystable intermittent switch which is not subject to faulty operation dueto vibration or shock.

It is an additional object of this invention to provide such improvedapparatus which will not be subject to atmospheric conditions but willoperate satisfactory at high altitudes and with extreme temperature andhumidity variations.

it is another object of this invention to provide improved timingapparatus which is of extremely light weight and occupies relativelylittle space.

It is a further object of this invention to provide timing apparatus inwhich the actuating and deactuating currents .are substantiallyadjustable whereby the periodicity ot' intermittent pulsing isestablished.

Additional objects of this invention will be manifest from thedescription, accompanying drawings, and appcnded claims.

In carrying out this invention in one form, a switch mechanism isprovided which is actuated by the elongation of a pretensioned thermallyexpandable wire. More particularly, one form of this invention comprisesa normally closed heating circuit which will cause the extension of saidthermally expandable wire to open the circuit whereby cooling will beeffected to once again complete .said circuit, causing continuousintermittent operation of :the associated electrical contacts.

For a more complete understanding of the invention tion.

v arsenal Patented June 5, 1956} ice reference should be made to theaccompanying drawings, wherein Figure 1 is an isometric view of oneembodiment of this invention;

Fig. 2 is a plan view of said embodiment;

Fig. 3 is a partial view in elevation showing the wire in its unheatedstate and the heating circuit closed;

Figure 4 illustrates the same portions of the structure as Fig. 3, butin the actuated position; and

Fig. 5 illustrates the apparatus after the wire has substantiallycooled, creating a tension tending to complete the heating circuitthrough the contacts.

Referring now to the drawings, and more particularly to Fig. 1, oneapparatus ll, illustrative of this invention, is shown. The apparatusincludes a base member 12 which is adapted to be fastened to chassis orother frame for electrical equipment. Base member 12 is of an L- shapeand is adapted to receive a pair of mounting screws 1;? which willsupport the remainder of the structure in a vertical position. While theapparatus is here shown vertically mounted, this device does not rely ongravitational forces for its operation and may therefore be operated inany desired position with equally satisfactory results.

Supported by the mounting screws 13 are a plurality of insulatingspacers 28, 29, Ell, a pretensioned spring member 15, a magnet support14, and a contact support 19. The spring member 15 at its lowerextremity forms an electrical terminal in adapted to receive one or moreconductors connected to associated equipment which are to be energizedintermittently. Attached to the upper portion of spring member is is anelectrically conductive thermally expandable wire 17. Wire 17 willnormally be tensioned to support spring member 3.5 in an actuated posi-This wire may be secured to the spring member 15 by any convenient meansbut is here shown attached by brazing. The wire 17 should be chosen ofsome material which will expand when heated so that the tension exertedby wire 17 will be'relieved, allowing spring member 15 to assume itsnormal position. Wire 3? is secured at its other end to a threadedterminal 318 which is retained in a bracket 19 whichis also held inplace against the insulating members 29 by the mounting screws 13. Thethreaded terminal 18 is movable in'a bushing 21 of an insulatingmaterial so that bracket 19 is electrically isolated from terminal 13.The magnet support 14 extends upwardly to support a permanent magnet 22;which is mounted in such a position that spring ltd, which has a softiron bar 23 mounted thereon, will be attracted to said magnet againstthe tension of wire 17. Vertical support lid is secured to bracket 19 byany convenient means and is adapted to support an adjustable contact 25which is threadedly mounted in a metallic bushing 21) to form anelectrical terminal. This terminal bushing 243 is, in turn, mounted inan insulating bushing 27 whereby terminal 25 is electrically isolatedfrom support as. Terminal 25 is adapted to engage a Contact 26 which issecured to spring member 315, and when these contacts are engaged twocircuits are completed, one for heating the wire 17 and a second forcompleting any desired external circuits connected to terminal to, aswill be explained in greater detail hereinafter.

Figs. 3, 4 and 5 illustrate the sequential steps in a single operationof this apparatus. in Fig. 3 the apparatus is shown in its actuatedposition with spring 15 moved to its extreme position under the tensionof wire 17 so that contact 26 is in engagement with the adjustableterminal 25. in this position there will normally be a predeterminedvoltage applied between bushing 24? and terminal 13 which will cause aheating current to flow. The path of this current will be from bushing2% through adjustable contact 25 and contact 26, spring member 15, wire17, to terminal 18. This heating current will raise the temperature ofWire 17 an amount determined by the character of the wire. Wire 17 willgenerally be of a fine gauge and composed of some material, such asNichrome, which has a high thermal coefiicient of expansion and canwithstand high temperatures without mechanical failure. Therefore, avery small current flowing in wire 17 for an extremely short time willcause it to expand sufiiciently so that the spring under its own tensionwill cause contact 26 to move to the right, leaving contact 25, at whichtime the heating circuit just described will be opened. However, in sucha wire there is a suificient thermal delay that it will continue toexpand for a limited time after the circuit is broken and will thusallow spring 15 to continue to move to the right. To augment thismotion, permanent magnet 22 and the associated iron shorting bar 23 areprovided. As the spring 15 moves to the right, magnet 22 will attractshorting bar 23, as best shown in Fig. 4, and will cause the heatingcircuit to remain open for a substantial period of time determined bythe relative magnitudes of the tension of wire 17, the tension of spring15, and the strength of permanent magnet 22. The particular embodimentherein shown has an adjustable repetition rate of between three andfifteen cycles per second.

As the wire 17 begins to cool it will once again contract, applying alateral force to spring member 15 tending to return it to its positionwhereby engagement of contact 26 with terminal 25 is effected. However,the force of magnet 22 on the shorting bar 23 will oppose the motion andwill cause spring 15 to assume the tortuous shape illustrated in Fig. 5.Ultimately the construction of wire 17 will create sufiicient force tobreak the magnetic circuit and allow spring 15 to once again move to theleft, thus causing contact 26 to engage terminal 25 and complete theheating circuit. When this heating circuit is completed once again, thecycle of events just described will recur, causing an intermittentreciprocating motion in spring member 15.

Terminal 18 is mounted for vertical adjustment so that the tension whichis applied by wire 17 to spring member 15 can be critically adjusted.This will determine the precise current necessary to break the heatingcircuit and will also affect the period of time necessary for onecomplete cycle of operation. Additionally, terminal 25 is provided witha threaded adjustment so that a pre-tension can be applied to the springmember 15 which will result in continued engagement for small rises oftemperature for wire 17 but a rather sudden action of spring member 15when the wire 17 reaches a predetermined temperature. This quick action,in combination with the snap action provided by permanent magnet 22 uponremaking the heating circuit, is very desirable in that it decreasesarcing and burning on the switch contacts, thus greatly prolonging thelife of the switch mechanism.

In addition to completing and breaking the heating circuit abovedescribed, this device is also adapted to make and break any desiredcircuits which are connected to terminal 16. Terminal 16 is an extensionof the spring member 15, as shown best in Fig. 1, and is adapted toreceive a plurality of conductors. In aircraft operation it is oftendesirable to have various intermittent alarms, such as flashing lights,whereby a pilot or crew member is apprised of various dangerouscircumstances aifecting the operation of the aircraft. Such circuitswould be completed through terminal bushing 20, adjustable contact 25,contact 26, and spring member 15, to terminal 16.

While in the illustrations herewith this apparatus is shown havingrather large dimensions to best illustrate the principles involved, itshould be understood that any size and dimensions could be assumed, andit is usually desirable that the dimensions be extremely minute. Bymaking all of the parts of small size and providing spring member 15with a small mass and relatively high elasticity, a wire 17 of extremelyfine diameter can be utilized. By way of example, in one embodiment ofthis invention a Nichrome wire with a diameter of .005 inch is utilizedfor controlling the switch member and thereby a current of the order of.l ampere is sufiicient to heat wire 17 and effect an opening ofcontacts 25 and 26.

Thus it can be seen that circuit control apparatus is here taught whichcan control various apparatus intermittently at any desired timeinterval with extremely small actuating currents. Apparatus is furtherprovided which is not subject to faulty operation under adverse weatherand atmospheric conditions and is not subject to damage resulting fromsevere shocks and vibrations.

Without further elaboration, the foregoing will so fully explain thegist of my invention that others may, by applying current knowledge,readily adapt the same for use under varying conditions of service,without eliminating certain features, which may properly be said toconstitute the essential items of novelty involved, which items areintended to be defined and secured to me by the following claims.

1 claim:

1. In electrical timing apparatus, an elongated longitudinallydeformable resilient member fixed at one end,

the free end having an actuated position and a normal unactuatedposition, an electrical contact mounted in spaced relation to the freeend of said resilient member to be engaged thereby, magnetic meansdisposed adjacent said free end to maintain said resilient member in theunactuated position, and a flexible conductor having a substantialthermal ex ansion and having one end thereof secured to a point on saidresilient member intermediate said fixed end and said free end and theother end fixed in spaced relationship to said resilient member, saidflexible conductor being normally tensioned to maintain said resilientmember in the actuated position under longitudinal tension whereby thethermal expansion of said conductor will cause said resilient member tomove to the unactuated position to be maintained there by said mag neticmeans.

2. In electrical timing apparatus, an elongated longitudinallydeformable resilient member having a free end movable between anactuated position and an unactuated position and having one end fixed toform an electrical terminal, an electrical contact mounted in spacedrelation to the free end of said resilient member to be engaged thereby,magnetic means disposed adjacent said free end to maintain saidresilient member in the unactuated position, and a flexible conductorhaving a sub stantial thermal coefficient of expansion and having oneend thereof secured to a point on said resilient member intermediate thefree end and said fixed end and the other end fixed in spaced relationto said resilient member to normally maintain said resilient memberunder longitudinal tension and to form a conductor terminal, whereby anelectric current flowing from said contact member to said conductorterminal will cause the thermal expansion of said conductor and a motionof the resilient member to the unactuated position.

3. In electrical timing apparatus, an elongated longitudinallydeformable resilient member having a free end movable between anactuated position and an unactuated position and having one end fixed toform an electrical terminal, an electrical contact mounted in spacedrelation to the free end of said resilient member to be engaged thereby,magnetic means mounted in spaced relationship to the free end of saidresilient member to maintain said resilient member in the unactuatedposition, a movable terminal adjustably mounted in spaced relation tothe fixed end of said resilient member, and a flexible conductor havinga substantial thermal coefficient of expansion and having one endthereof secured to a point on said resilient member intermediate saidfree end and said fixed end and the other end thereof secured to saidmovable terminal whereby said resilient member is normally maintainedunder tension and a predetermined magnitude of electric current flowingfrom said contact member to said movable terminal will cause the thermalexpansion of said conductor and a motion of said resilient member to theunactuated position.

4. In electrical timing apparatus, an elongated longitudinallydeformable resilient member having a free end movable between anactuated position and an unactuated position and having one end fixed toform an electrical terminal, an electrical contact mounted in spacedrelation to the free end of said resilient member and adjustable withrespect thereto to determine the actuated position of said resilientmember, magnetic means mounted in spaced relationship to the free end ofsaid resilient member to maintain said resilient member in theunactuated position, a movable terminal adjustably mounted in spacedrelation to the fixed end of said resilient member, and a flexibleconductor having a substantial thermal coeflicient of expansion andhaving one end thereof secured to a point on said resilient memberintermediate said free end and said fixed end and the other end thereofsecured to said movable terminal whereby said resilient member isnormally maintained under tension and a predetermined magnitude ofelectrical current flowing from said contact member to said movableterminal will cause the thermal expansion of said conductor and a motionof said resilient member to the unactuated position.

References Cited in the file of this patent UNITED STATES PATENTS1,946,894 Brogger Feb. 13, 1934 1,979,349 Schmidinger Nov. 6, 19342,243,563 Hottenroth May 27, 1941 2,299,767 Schmidinger Oct. 27, 19422,302,399 Stimson Nov. 7, 1942 2,312,974 Owens Mar. 2, 1943 2,319,241Leuthold May 18, 1943 2,512,268 Eros et a1. June 20, 1950 2,659,787Prickett Nov. 17, 1953

